Process for preparing copolymers of styrene and divinylbenzene



Patented Jan. 5, i954 TAT E S UNITED TNT QFFIC' PRO'QESS FOR PREPARKNG COPOLYMERS- (9F STYRENE AND DIVINYLBENZENE Robert N. Harvard and .loyce EllyflraifordPark,

Manchester, England, assignors to Petrocarbon Limited, London, England No Drawing; Application December 10, 1951,

Serial- No. 260948.

Claims priority, application Great Britain' December 21, 1950 7 Claimsr (Cl. 260 4881.).

This invention relates to the production of copolymers of styrene and divinylbenzenep Such copolymers may be produced by the copolymerisation of styrene with a.- pure or substantially pure divinylbenzene, but they are more generally formed for commercial purposesirorn styrene and the commercially available concentrate of divinylbenzene which contains an appreciable proportion of ethyl-vinylbenzene. Though in the latter case'the products would possibly be more correctly termed-ternary polymers, they are usually referred to as copolylners polymerisation process but it has-now been found that satisfactory and consistent results may be obtained by the use of bentonite as a suspension stabiliser, aided by the presence in the aqueous suspension medium of gelatin and a soluble, substantially neutral inorganic salt.

The invention thus consists in a process for the production of copolymers of styrene and divinylbenzene by a suspension polymerisation process which comprises polymerising a. mixture of styrene and divinylbenzene whilst it is maintained dispersed in an aqueous medium in which there are also dispersed finely divided particles of hentonite and in which there has been dissolved gelatin and a substantially neutral inorganic salt.

The ratio by weight of the mixture of monomers to water in the suspension in the process or" the invention is preferably from 1:5 to 3:2.

The polymerisation is preferably carried out in the presence of a monomer-soluble polymerisation catalyst such, for example, as benzoyl peroxide, tertiary butyl perbenzoate, or azo-bisisobutyronitrile and preferably at a temperature of from 70 to 120 C.

In the process of the invention, the amount of bentonite present in the suspension is preferably from 0.001% to 0.05% by weight of the whole system; the amount of gelatin present is preferably from 0.0005 to 0.01% by weight of the whole of the invention are the substantially neutral salts of the allealior-alkaline earth metals with anions oI" valency 1 or 2. Examples are potassium chloride," sodium chloride, potassium sulphate, sodium sulphate, ca-lcienr chlorideand potassium thiocyanate.

By substantially neutral salt is meant a salt which in solution in wateri-n the concentrations used in the process has a-pH-value between=5 9 and preferably between 6 and- 8.

The divinylben-zene used inthe process or" the invention be the commercially available divinylbenzene concentrate, which normally contains approximately 50% by weight of 'nylbenzene and a somewhat smaller proportion oi ethylvinylbenzene or a purer form of divinyibenzene.

The following-examples illustrate the process of the invention:

Example 1 2'76 cos. of demineralised water l40 ccsof styrene and 24 cos. of divinylbenzene were stirredtogetherin a 500 cc. flask. fitted with a reflux con denser and heated to C. 0.4 gm. of benzoy peroxide was then added and the stirring and heating continued. After 10 minutes, bentonite in suspension in water was added, one minute later a solution of potassium chloride in water was added and one minute after that a solution of gelatin in water was added. The amounts of bentonite, potassium chloride, and gelatin dded in this manner were such that they constituted respectively by weight of the total system 0.02%, 0.05%, and 0.004%. The additional water added with the bentonite, potassium chloride gelatin was 20 cos.

Stirring and heating were continued for 9 when hard pearls or beads were formed.

The product was found to be eminently suitable for the production of ion exchange resins.

Example 2 320 cos. of deinineralised water, cos. of styrene and 40 cos. of divinylbenzene were stirred together in a 500 cc. flask, fitted with a reflux condenser and heated to 90 C. 0.54 gm. of the polymerisation catalyst sold under the trade name Porofor 254 (believed to be an azonitrile catalyst) was then added and the stirring and heat" ing continued. After ten minutes, bentonite in suspension in water was added one minute later a solution of potassium chloride in water was added and one minute after that a solution of gelatin in water was added. The amounts of bentonite, potassium chloride, and gelatin added in this manner were such that they constituted respectively by weight of the total system 0.02%, 0.05%, and 0.004%. The additional water added with the bentonite, potassium chloride and gelatin was 20 cos.

Stirring was continued for 2 hours at 90 C., followed by stirring for 7 hours at 98 C. Hard pearls or beads were obtained.

Example 3 140 cos. of monomer, consisting of 57 parts by volume of styrene to 5 parts by volume of divinylbenzene, and containing 0.4 gm. of benzoyl peroxide, were added to 280 ccs. water, stirred at 840 revs/min. by a V-shaped stirrer, in a. 500 cc. flask, situated in an oil bath at 91 C.

After 15 minutes, 0.36 gm. bentonite were added. After 16 minutes, 4.05 cos. of a 5% solution of potassium chloride were added and after 17 minutes 9.7 ccs. of a 0.5% solution of gelatin were added.

The mixture was stirred for 12 hours when fine .hard pearls were obtained.

The divinylbenzene used in the above examples was a commercial concentrate having the following analysis:

Per cent by weight Divinylbenzene 48.0 Ethylvinylbenzene 42.1 Diethylbenzene 9.1 Naphthalene 0.5

Tertiary butyl catechol (inhibitor) 0.1

The bromine No. was 167.7.

The bentonite used in each case was that sold under the trade name Bentonil C.

The size of the beads produced by the process of the invention may be varied by varying the quantity of bentonite and/or gelatin and/or inorganic salt present. Thus by increasing the quatities of these ingredients the size of the beads formed is decreased.

The products of the process have been found to be eminently suitable for use, after suitable chemical treatment, as ion exchange resins. They may also be used for forming reflecting surfaces such as are used on road signs and cinema screens and for decorative purposes. A coloured product may be obtained by the addition of suitable dyes prior to polymerisation.

We claim:

1. A process for the production of copolym s of styren and divinylbenzene by a suspension polymerisation process, which comprises polymerising a mixture of styrene and divinylbenzene whilst it is maintained dispersed in an aqueous medium in which there are also dispersed finely divided particles of bentonite and in which there has been dissolved gelatin and a substantially neutral inorganic salt selected from the class consisting of the substantially neutral inorganic salts of alkali metals and alkaline earth metals.

2. A process as claimed in claim 1 in which the divinylbenzene is in the form of a commercial concentrate of divinylbenzene containing an appreciable proportion of ethylvinylbenzene.

3. A process as claimed in claim 1 in which the amounts of bentonite, gelatin, and inorganic salt present in the aqueous medium are from 0.001 to 0.05%, from 0.0005 to 0.01% and from 0.01 to 0.2% by weight of the whole system respectively.

4. A process as claimed in claim 1, in which the ratio by weight of the mixture of monomers to water in the aqueous medium is from 1:5 to 3:2.

5. A process as claimed in claim 1 in which the p ymerisation is carried out in the presenc of a polymerisation catalyst.

6. A process as claimed in claim 1 in which the polymerisation is carried out at a temperature from to C.

7. A process as claimed in claim 1 in which the said neutral salt is potassium chloride.

ROBERT N. HAWARD. JOYCE ELLY.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. A PROCESS FOR THE PRODUCTION OF COPOLYMERS OF STYRENE AND DIVINYLBENZENE BY A SUSPENSION POLYMERISATION PROCESS, WHICH COMPRISES POLYMERISING A MIXTURE OF STYRENE AND DIVINYLBENZENE WHILST IT IS MAINTAINED DISPERSED IN AN AQUEOUS MEDIUM IN WHICH THERE ARE ALSO DISPERSED FINELY DIVIDED PARTICLES OF BENTONITE AND IN WHICH THERE HAS BEEN DISSOLVED GELATIN AND A SUBSTANTIALLY NEUTRAL INORGANIC SALT SELECTED FROM THE CLASS CONSISTING OF THE SUBSTANTIALLY NEUTRAL INORGANIC SALTS OF ALKALI METALS AND ALKALINE EARTH METALS. 